1. Field of the Invention
The present invention relates to a digital cable television broadcasting receiver capable of downloading the conditional access software in the digital cable television broadcasting that makes the conditional access.
2. Related Art of the Invention
In the satellite broadcasting or the digital broadcasting of cable television, the conditional access is widely employed for charging management and contents protection. A conditional access method in the digital broadcasting was described in ARIB STD-B25 in Japan. A conditional access function on the receiver side is implemented on an IC card, which is a B-CAS card in the satellite broadcasting or a C-CAS card in the cable television broadcasting. In the United States, the conditional access function is mounted in a module (on-board) as the built-in function on the receiver.
A scheme of the conditional access is implemented by sending an ECM (Entitlement Control Message) and an EMM (Entitlement Management Message) from a conditional access control facility installed at head-end to the receiver to be controlled. The EMM encrypts a work key by a master key (device key) allocated to each receiver or each conditional access card, and the conditional access function of each receiver or each conditional access card involves decrypting the work key sent with the EMM using its own master key and decoding the ECM sent together with video data to obtain a scramble key for unscrambling.
FIG. 5 (a) is a block diagram showing a configuration example of the conventional IC card, and FIG. 5 (b) is a block diagram showing the configuration of the conventional modules. A conditional access control head-end 4 sends the EMM and the ECM on a TS (Transport Stream) to a conditional access IC card 6 or a conditional access module 7 mounted on a receiver 1. A conditional access IF part is an interface part to the conditional access IC card 6 or the conditional access module 7 contained in the receiver 1.
However, there are increasing demands for a VOD (Video On Demand) and the next generation bi-directional services. For the conditional access method, it is required to cope with those new services flexibly. Also, with the conventional IC card or built-in feature, the software cannot be improved even if the conditional access function has a problem. Also, in the type where the conditional access function is built in, it is required to cope with the conditional access function for plural vendors, resulting in a problem that the receiver can not be made common. Therefore, supposedly, a new scheme for downloading and updating the conditional access function (software) held in the receiver from the head-end is required.
Since a conditional access software has a high confidentiality, high security is required for downloading. Therefore, an authentication between a downloader and an IC card chip and a secure communication by the encryption of data are requisite. For the procedures of the authentication and the encryption, an authentication using a hash function such as de facto MD5 and SHA-1 and so on and a method using an encryption algorithm such as AES and RSA and so on can be uniquely built.
On the other hand, in the IC card such as a credit card, plural applications such as the ID card are generally mounted, besides the conventional credit purchase. In such IC card, the applications need to be updated. JAVA (registered trademark) card with a global platform (GlobalPlatform) technique capable of downloading the application is marketed, whereby the secure download technique has been established. The specifications of the global platform are publicized in a global platform consortium.
FIG. 6 is a block diagram of the global platform. The IC card chip 2 has an execution environment 28 including the software for a card OS, JAVA (registered trademark), VM (Virtual Machine), and a global platform API (application interface), in addition to a hardware environment of CPU and memory. Downloading the application onto the IC card chip 2 corresponding to the global platform technique is made by establishing a secure communication path between a global platform card manager 21 mounted on the IC card chip 2 and a card issuer 31 that is the download host, based on an encryption key preset for the global platform card manager 21, and downloading the application software 29 via the global platform card manager 21. When the secure communication path is established, the global platform card manager 21 sends the authentication information (global platform identification number) to the card issuer 31 that is the download host to make the authentication, employing the preset encryption key.
On the other hand, if the IC card chip 2 is used and the global platform is not used, the portion corresponding to the card manager 21 is implemented as a dedicated application on the card OS. In this case, the interface between the downloader corresponding to the card issuer 31 or application service provider 41 and the card manager 21 is specific depending on the card OS. (refer to Japanese Patent Application Laid-Open No. 2001-119357, Japanese Patent Application Laid-Open No. 2004-13728, Conditional access method in digital broadcasting ARIB STD-B25 and the GlobalPlatform Card Specifications (by the GlobalPlatform consortium)).
If a mechanism of securely downloading the conditional access software of the digital cable television to the IC card or IC card chip can be built, it is possible to download and update said new service, which is very beneficial.
Also, if the IC card or IC card chip corresponding to the global platform technique is employed for downloading the conditional access software of the digital cable television, the open chip and software environment can be utilized, in which the scheme for downloading is assured to be secure, and established with the technique on the operational side, which is very convenient.
However, a number of conditional access facilities of the digital cable television exist in every broadcasting district, and its operation is made separately from a development company of the conditional access software. In the case of the cable television, it is common that the cable operator operates this television. Accordingly, a scheme for hiding the conditional access software from the operator is required from the nature of the conditional access software. For example, the global platform technique assumes only the configuration that the card issuer downloads the application, or that the application provider directly downloads the application, whereby the scheme of IC card corresponding to the global platform technique can not be directly employed in the cable television scheme in which the head-end operator that is not the application provider downloads the conditional access software of the application.
In the case where the conventional conditional access function was mounted in the built-in type, the identification number of conditional access was set when the function was built in, and managed integrally with the identification number of the receiver, whereby individual receivers could be controlled. Also, in the case of the IC card type, the identification number of conditional access is set in advance in the IC card, and the management number of the IC card is managed, whereby the individual IC card can be identified. However, to download the conditional access software to the IC card or IC card chip, and to control the conditional access from the head-end in accordance with the contract condition of the subscriber, it is required that the conditional access control software of the head-end identifies the conditional access software of each receiver and sends the EMM to the conditional access software that is the downloaded application software. For example, it is only the individual encryption key of the global platform card manager that is defined in the global platform, and no identification information for the conditional access software that is the global platform application is defined. Accordingly, the scheme for the IC card corresponding to the global platform technique can not be directly employed in the scheme for the cable television, whereby it is required to provide a scheme for newly setting the identification information of the conditional access reception software to be downloaded and the individual key (device key) for conditional access in association with the individual receiver.
Also, when secure communication is performed between the downloader and the IC card chip, it is required to set the encryption key in the card manager. However, in the case of the credit card, for example, the card issuer can consistently set the encryption key in the IC card, issue the card and download the application at one site in high security. However, in the case of the cable television, a cable operation company or a key issuance management company of neutral authentication authority is supposed to set the encryption key to the IC card chip, but the IC card chip is supplied to plural receiver makers and packaged, and provided to the subscriber with the receiver. Since it is difficult to set the encryption key to the global platform card manager in the light of the operation and the security, after packaging the IC card chip in the receiver, it is required to set in advance the encryption key in a state of the IC card chip. However, if the scheme for the IC card corresponding to the global platform technique is directly employed in the scheme for the cable television, the operation of the IC card chip possibly becomes complex.
Also, when the conditional access software is downloaded to the IC card chip, the download of the application occurs into the IC card chip which is connected to the download host at a moment when the IC card is inserted into a card reader. In the case of the digital cable television receiver, it is always supposed that the receiver makes an issuance even when there is a modem such as DOCSIS, whereby it is not possible to make the connection from the download host. The receiver may be periodically connected to the download host to download the application. But the number of connected receivers is supposedly from about hundred thousands to one million per head-end, it is unrealistic to wait for the connection from the receiver to download the application. Accordingly, the scheme for the IC card corresponding to the global platform technique can not be directly employed in the scheme for the cable television, for example, whereby it is required to provide a new scheme for allowing the connection from the download host to the desired receiver.